Method for the reduction of the degree of shrinkage of hydraulic binders

ABSTRACT

On object of the present invention is an agent for the reduction of the degree of shrinkage in hydraulic binders, whereby said comprises an alkanolamine of formula R-NH-(AOH) wherein R is hydrogen or a linear or branched aliphatic or cyclic C1-C6-alkyl group, and A is a C2H4-group or C3H6-group, alone or in combination with hydroxy compounds and/or ethers. Furthermore a method for the reduction of the dry shrinkage of binders such as cement, admixed cement, puzzolanas and thereof produced mortars and concretes by means of such a shrinkage reducing agent is described.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 09/493,266,filed on Jan. 28, 2000, now U.S. Pat. No. 6,398,866. This applicationclaims the priority of Swiss Patent Application 0165/99, filed Jan. 29,1999, the disclosure of which is incorporated herein by reference in itsentirety.

BACKGROUND OF THE INVENTION

The invention relates to an alkanolamine comprising agent for thereduction of the degree of shrinkage in hydraulic binders (shrinkagereducing agent), whereby said agent contains or consists of specificalkanolamines of formula R—NH—(AOH) alone or in combination with hydroxycompounds and/or ethers. Furthermore, a method for the reduction of thedegree of dry shrinkage of binders such as cement, mixed cement,puzzolanes and thereof produced mortars and concretes by means of such ashrinkage reducing agent is described.

During the entire curing process, hydraulic binder systems pass throughseveral steps. The first change in dimension prior to setting,comprising plastic shrinkage, can be compensated by the hardeningcomposition and the therefrom resulting forces can be corrected.However, volume changes due to loss of water in the cured state can nolonger be compensated by the system. Thus, such changes, in spite oftheir low magnitude, lead to the formation of cracks and deformations insaid composition. Due to said cracks, the attack of the cement and/or—ifpresent—steel reinforcements by damaging substances are facilitated andpenetrating water can lead to the destruction of the structure due tofreezing. All these problems lead to a significant reduction of the longtime durability of a building due to said dry shrinkage.

Hitherto, already several substances are known that reduce the dryshrinkage of concrete. The most common of them are glycols andpolyglycols as well as glycol ethers and polyglycol ethers. All of themare substances that can reduce the degree of shrinkage. Furthermore,types of substances exist that compensate the resulting volume reductionby expansion.

Substances falling under the second class are substances forming gasesin an alkaline medium such as hydrazine compounds (nitrogen) or aluminumpowder (hydrogen) as well as iron powder, the activity of which is basedon a volume enhancement due to formation of iron oxide (rust).Furthermore, also calcium sulfoaluminates that are precursors of thevoluminous ettringite and burned calcium oxide are used. All saidsubstances are powders and thus suffer disadvantages in connection withtheir dosing. Furthermore high percentage of said substances must beadded. Gas forming agents per se have the disadvantage that said gas canalready be formed prior to the addition of concrete, and the generationof hydrogen in general is considered as very critical on a productionsite.

The cementituous precursors are very much dependent from the actualconditions, such as cement composition, temperature, environmentalhumidity and degree of hydration of the cement, and can lead to aspontaneous expansion in the cured state. The also promoted formation ofettringite can affect the durability of such a building.

In general it can be said that by said expansion effecting agents only acorrection of the starting point of the thereon following dry shrinkagecan be achieved. The magnitude of the degree of shrinkage as suchremains the same and therewith deformations as mentioned abovenevertheless can lead to damages.

Several substances comprising hydroxyl groups are already known aspossible shrinkage reducing agents. For example lower alcohols areproposed (JP 1-129578/89) that, however, raise problems due to their lowpoint of ignition.

Higher molecular systems, such as adducts of alcohol and alkylene oxideor adducts of alkylphenol and alkylene oxide (e.g. JP 37259/81 or10947/87) have to be added in large amounts in order to achieve thedesired result.

Also several small polyols have already been proposed. In 1987 Schulzementioned terminal hydroxyl groups comprising compounds of the typeC_(n)H_(2n)(OH)₂ as efficient (EP 0 308 950) and several Japanesepublished applications (e.g. 55-027819 or 06-072748) refer to similartypes or special cases. Recently, in particular secondary and tertiaryalkanediols were further investigated and found to be efficient.

Ether comprising diols have already generally been mentioned asshrinkage reducing agents by Goto in 1985 (U.S. Pat. No. 4,547,223).More specifically defined types have reached greater interest and aredescribed as effective (WO 95/30630 and WO 96/27563 to Shawl as well asWO 96/27564, WO 96/27565 and U.S. Pat. No. 5,618,344 to Berke).

As further classes of substances water-soluble amino resins incombination with metal salts of fatty acids are mentioned by Okuno in1989 (EP 0 359 068). In 1994 good results with amides, or generallyformyl compounds, respectively, are reported by Abdelrazig in U.S. Pat.Nos. 5,326,396 and 5,326,397.

With regard to alkanolamines U.S. Pat. No. 3,583,880 teaches that theshrinkage of porous products can be reduced by the application of i.a.alkanolamines to already produced inorganic bodies. In 1995 Abdelrazigdescribed (in U.S. Pat. No. 5,389,143) α,β-alkanolamines that on the onehand can effectively reduce the shrinkage that, however, on the otherhand, are very expensive. The alkanolamines described by Abdelrazig showthe following general formula

wherein R₁ and R₂ independently of each other represent hydrogen or alinear or a branched alkyl group. R₃ and R₄ can also independently fromeach other be hydrogen or a linear or a branched alkyl group with theproviso that R₃ and R₄ together have at least two carbon atoms so thatin particular R₃=H and R₄=H are excluded.

All the mentioned shrinkage reducing agents have one or moredisadvantages. In view of their high dosage and/or their expensiveproduction, they are uneconomical, due to their high surface activity,they destroy the effect of air entraining agents, due to theirinflammability/point of ignition they cannot suitably be used atproduction sites, or they drasticly retard the development of strengthsof cementituous systems.

BRIEF SUMMARY OF THE INVENTION

Hence it is a general object of the present invention to provide ashrinkage reducing agent as well as a method for the reduction of thedegree of shrinkage of hydraulic binders, that avoids theabove-mentioned disadvantages at least in part. It is in particular anobject of the present invention to provide a shrinkage reducing agentthat on the one hand is cheap, easily producible, allows unproblematichandling and furthermore develops a good shrinkage reducing effect.Furthermore, the shrinkage reducing agent should not affect the frostresistance of the resulting concrete in that, because of the addition ofthe shrinkage reducing agent, the amount of air present in the concreteis markedly reduced. A further object of the invention is to provide amethod for the reduction of the degree of shrinkage of concrete that inparticular is cheap and expedient. Said goals are achieved according tothe independent claims. Preferred embodiments are mentioned in thedependent claims.

Now, in order to implement these and still further objects of theinvention, which will become more readily apparent as the descriptionproceedings, the agent for the reduction of the degree of shrinkage ofhydraulic binders contains or consists of

a) at least one alkanolamine of formula I

R—NH—(AOH)  I,

wherein R is hydrogen or a linear or a branched aliphatic or cyclicC₁-C₆-alkyl group, and A is a C₂H₄- or C₃H₆-group, alone or incombination with

b) at least one hydroxy compound and/or

c) at least one ether compound.

Another aspect of the present invention is a method for the reduction ofthe degree of shrinkage of hydraulic binders such as cements accordingto Euronorm EN 197 in pure form or as admixture with latent hydraulicbinders such as fly ash, blast furnace slag, burned oil shale, naturalpozzolanas or silicafume or inert fillers such as stone powder, as wellas thereof produced mortar or concrete, characterized in that a bindercomprising mixture is additionally admixed with a shrinkage reducingagent according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The inventive agent for the reduction of the degree of shrinkage(shrinkage reducing agent) of hydraulic binders contains or consists of

a) at least one alkanolamine of formula I

R—NH—(AOH)  I,

wherein R is hydrogen or a linear or branched aliphatic or cyclicC₁-C₆-alkyl group, preferably C₃-C₆ alkyl group, and A is a C₂H₄- orC₃H₆-group, alone or in combination with

b) at least one hydroxy compound and/or

c) at least one ether compound.

In a preferred embodiment the shrinkage reducing agent contains orconsists of

a) about 1-100% by weight of at least one alkanolamine of formula I aswell as

b) about 0-90% by weight of at least one hydroxy compound and/or

c) about 0-90% by weight of at least one ether compound.

In an even more preferred embodiment, the shrinkage reducing agentcontains or consists of a combination of

a) about 5-40% by weight of at least one alkanolamine of formula I aswell as

b) about 0-90% by weight of at least one hydroxy compound and/or

c) about 0-90% by weight of at least one ether compound, whereby the sumof b) and c) in a preferred embodiment is at least about 60% by weight.

In a most preferred embodiment, the shrinkage reducing agent contains orconsists of a combination of

a) about 10-40% by weight of at least one alkanolamine of formula I aswell as

b) about 0-90% by weight of at least one hydroxy compound and/or

c) about 0-90% by weight of at least one ether compound, whereby the sumof b) and c) is at least about 60% by weight.

Particularly preferred alkanolamines are selected from the groupcomprising N-propylaminopropanol, N-butylaminopropanol,2-(n-butylamino)-ethanol, 2-(t-butylamino)-ethanol,2-(cyclohexylamino)-ethanol, 2-amino-1-propanol. Thereby, thealkanolamines can be present as such but also as salts of an organic orinorganic acid or as salts of a mixture of said acids or as a mixture ofalkanolamines as such and at least one of their salts.

The alkanolamines used according to the present invention differ fromthose of Abdelrazig (U.S. Pat. No. 5,389,143) e.g. in the fact thatbesides of α,β-alkanolamines also α,γ-alkanolamines are applied, whilewith regard to the α,β-alkanolamines of formula I only those are appliedwherein A is a C₂H₄ or a C₃H₆ group. This selective feature with regardto the alkanolamines has the great advantage that only cheapalkanolamines are applied whereby, against all expectations,surprisingly also with these comparatively simple alkanolamines offormula I alone or, in an even extended manner, in combination with thehydroxy compounds b) and/or the ethers c) an excellent shrinkagereducing effect can be achieved.

The hydroxy compounds comprised in one embodiment of the inventiveshrinking reducing agent are preferably diols, in particular diolsselected from the group comprising 2,2-dimethyl-1,3-pentanediol,2,5-dimethyl-2,5-hexanediol, 2-ethyl-1,3-hexanediol, 1,6-hexanediol,1,5-pentanediol, hexyleneglycol, polypropyleneglycol.

The ether compounds comprised in one embodiment of the inventiveshrinkage reducing agent preferably are selected from the groupcomprising diethyleneglycol monobutylether, triethylenglycolmonobutylether, triethyleneglycol monomethylether, dipropyleneglycolmonobutylether, and ethoxylated neopentylglycol adduct.

The shrinkage reducing agent can be present as powder, or it cancomprise water and/or a non-aqueous solvent thus that it is present asdispersion or emulsion or solution. For dispersions, emulsions andsolutions it is preferred that the sum of a) and b) and c) is 50 to 80%by weight.

A further aspect of the present invention consists in a method for thereduction of the degree of shrinkage of hydraulic binders such ascements according to Euronorm EN 197 in pure form or as mixture withlatent hydraulic binders or inert fillers as well as thereof producedmortar or concrete. According to the method of the present invention ashrinkage reducing agent is added to a mixture comprising the binder,which shrinking reducing agent contains or consists of

a) at least one alkanolamine of formula I

R—NH—(AOH)  I,

wherein R is hydrogen or a linear or a branched aliphatic or cyclicC₁-C₆-alkyl group, preferably a C₃-C₆-alkyl group and wherein A is aC₂H₄-group or C₃H₆-group, alone or in combination with

b) at least one hydroxy compound and/or

c) at least one ether compound.

Latent hydraulic binders are e.g. fly ash, blast furnace slag, burnedoil shale, natural pozzolanas or silica fume and inert fillers are e.g.stone powder.

In a preferred embodiment, the shrinkage reducing agent is added to thebinder comprising mixture in an amount of 0,001-6,0% referred to theweight of the binder. Even more preferred is an amount of 1-3% by weightreferred to the weight of the binder of the shrinkage reducing agent inthe binder comprising mixture.

The shrinkage reducing agent can be applied as powder or dispersed oremulgated in water and/or in a non-aqueous solvent or dissolved in waterand/or in a non-aqueous solvent. The shrinkage reducing agent can beapplied premixed in one or more hydraulic binders or in dry mortar or inconcrete. The admixture of shrinkage reducing agent to the bindermixture can be performed during the production of the binder in thefactory either prior or during the grinding.

In a further preferred embodiment the shrinkage reducing agent can beadded to the dry binder or to the water admixed binder, mortar orconcrete in the factory, at the production site, in the mixing device,in the delivery pump or by means of a static mixing means with a powderdosing apparatus or a liquid dosing apparatus directly into the mixture.

A further aspect of the present invention is the use of an agentcontaining or consisting or

a) at least one alkanolamine of formula I

R—NH—(AOH)  I,

wherein R is hydrogen or a linear or branched aliphatic or cyclicC₁-C₆-alkyl group, preferably a C₃-C₆-alkyl group, and A is a C₂H₄-groupor a C₃H₆-group, alone or in combination with

b) at least one hydroxy compound and/or

c) at least one ether compound for the reduction of the degree ofshrinkage of hydraulic binders.

It was surprisingly found that with the above-mentioned inventiveshrinkage reducing agents the features related with the processing ofconcrete and mortar such as processability and strength, are not or onlyin a low degree influenced. Furthermore, in spite of the use ofshrinkage reducing agents, it is possible to produce concrete that ismade resistant to frost and defrosting salts by the incorporation of airpores by means of respective additives. A further advantage is theeconomy that is achieved by the application of low amounts as well asthe easy availability of the substances of the present invention.

The shrinkage reducing additives of the present invention can be presentand thus be applied as powder, dissolved in water or in combination withnon-aqueous solvents and/or other concrete admixtures such as waterreducers, high range water reducers, air entraining agents, corrosioninhibitors, silica slurries, dispersing agents etc. The admixtureusually is performed in solid or dissolved form directly into the mixingwater, to the cement, to the dry mixture or to the prepared concrete ormortar mixture.

In the following, the present invention is further explained by means ofexamples. Said examples are, however, by no means intended to in any wayrestrict the extent of the protection.

In the following examples the influence of alkanolamines alone or incombination with shrinkage reducing agents of the present invention isshown. As test mixtures for the performance of the examples mortars wereselected that are intended to simulate concrete. The mixtures werecomposed as follows:

Portland cement type CEM I 42.5 750,00 g sand 0-8 mm 3150.00 g water352.50 g high range water reducer on the basis of melamine 7.50 gshrinkage reducing agent 11.25 g.

Of this mixtures test bodies in prismatic form with the dimensions4×4×16 cm with incorporated plug were produced and thereon thedimensional changes were measured according to a norm, namely DIN 52450.The test bodies were stored at 20° C. and 95% relative humidity for thefirst 24 hours and then at 23° C. and 50% relative humidity.

EXAMPLE 1

This example shows the effect of a shrinkage reducing agent on the basisof alkanolamine on the changes of length after 28 days.

Additive Change of length after 28 days Reference (without shrinkage−0.55% reducing agent) Shrinkage reducing agent −0.31% 1 (consisting ofPROPA) PROPA = N-propylaminopropanol

This example shows that the application of 1,5% (w/w) of analkanolamine, referred to the weight of the cement, reduces the dryshrinkage for 40%. The two following examples show the effect ofalkanolamines in combination with diols or ethers, respectively.

EXAMPLE 2

Change of length Additive after 28 days Reference (without shrinkagereducing agent) −0. 55% Shrinkage reducing agent 2 (consisting of Ehdo)−0.37% Shrinkage reducing agent 3 (consisting of ^(t)Buea) −0.28%Shrinkage reducing agent 4 (^(t)Buea/Ehdo 1:2) −0.22% Ehdo =2-ethyl-1,3-hexanediol ^(t)Buea = 2-(tert.-butylamino)-ethanol

Ehdo=2-ethyl-1,3-hexanediol

^(t)Buea=2-(tert.-butylamino)-ethanol

EXAMPLE 3

Change of length Additive after 28 days Reference (without shrinkagereducing agent) −0.55% Shrinkage reducing agent 5 (consisting of TEGBu−0.36% Shrinkage reducing agent 6 (consisting of PROPA) −0.30% Shrinkagereducing agent 7 (PROPA/TEGBu 1:2) −0.25% TEGBu = triethyleneglycolmonobutylether PROPA = N-propylaminopropanol

TEGBu=triethyleneglycol monobutylether

PROPA=N-proplaminopropanol

As can be seen from the above two examples, the shrinkage reducinginfluence of the single components surprisingly is significantlyenhanced in a synergistic way by applying a combination of alkanolaminesand diols and/or ethers.

EXAMPLE 4

Change of length Additive after 28 days Reference (without shrinkagereducing agent) −0.55% Shrinkage reducing agent 5 (consisting of TEGBu/−0.35% Ehdo 1:1) Shrinkage reducing agent 6 (consisting of ^(t)Buea)−0.29% Shrinkage reducing agent 7 (^(t)Buea/TEGBu/Ehdo −0.24% 1:1:1)TEGBu = triethylenglycol monobutylether Ehdo = 2-ethyl-1,3-hexanediol^(t)Buea = 2-(tert.-butylamino)-ethanol

TEGBu=triethyleneglycol monobutylether

Ehdo=2-ethyl-1,3-hexanediol

^(t)Buea=2-(tert.-butylamino)-ethanol

As can be seen from the three above shown examples, the shrinkagereducing influence of the single components surprisingly issignificantly enhanced by the combination of alkanolamines and diolsand/or ethers in a synergistic way.

EXAMPLE 5

The mixture used in this example is based on the above described mortar,however, additionally 6 g of a tall oil resin based air entraining agent(comprising about 5% of said air entraining agent) (i.e. 0,8 percent byweight referred to the cement weight) were added.

Change of length Additive after 28 days Reference (without shrinkagereducing agent) −0.55% Shrinkage reducing agent 2 (consisting of Ehdo)−0.34% Shrinkage reducing agent 8 (consisting of 66% Ehdo −0.33% and 10%nBuea + 24% H₂O) Ehdo = 2-ethyl-1,3-hexanediol nBuea =2-(butylamino)-ethanol

Ehdo=2-ethyl-1,3-hexanediol

nBuea=2-(butylamino)-ethanol

Basically, no difference in the degree of shrinkage can be seen,however, the amount of substance in the combination of diol andalkanolamine is significantly smaller (shrinkage reducing agent 8comprises 24% water), which is reflected by the air content that isessential for frost resistant concretes.

Additive Air content Reference (without shrinkage reducing agent) 8.5%Shrinkage reducing agent 2 (consisting of Ehdo) 2.1% Shrinkage reducingagent 8 (consisting of 66% Ehdo and 5.8% 10% nBuea + 24% water)

As can be seen from the above results, by the combination of analkanolamine with a diol, the loss of air content obtained with the diolalone, is reduced, without affecting the shrinkage behavior.

EXAMPLE 6

In this example it is shown that a shrinkage reducing agent of thepresent invention only minimally affects the strength development.

Compressive strength Additive 1 day 28 days Reference (without shrinkagereducing agent) 24 N/mm² 49 N/mm² Shrinkage reducing agent 2 (consistingof Ehdo) 16 N/mm² 45 N/mm² Shrinkage reducing agent 8 (consisting of 66%21 N/mm² 47 N/mm² Ehdo and 10% nBuea + 24% H₂O) Ehdo =2-ethyl-1,3-hexanediol nBuea = 2-(butylamino)-ethanol

Ehdo=2-ethyl-1,3-hexanediol

nBuea=2-(butylamino)-ethanol

While the application of a diol alone leads to a significant reductionin strength after one day, mortars produced with a shrinkage reducingagent of the present invention show an acceptable strength.

While there are shown and described presently preferred embodiments ofthe invention, it is to be distinctly understood that the invention isnot limited thereto but may be otherwise variously embodied andpracticed within the scope of the following claims.

What is claimed is:
 1. A method for the reduction of the degree ofshrinkage of hydraulic binders in pure form or as admixture with latenthydraulic binders or inert fillers, as well as thereof produced mortaror concrete, said method comprising admixing a shrinkage reducing agentand a hydraulic binder or composition containing a hydraulic binder orinert fillers, said shrinkage reducing agent comprising: a) at least onealkanolamine of formula I R—NH—(AOH)  I, wherein R is hydrogen or alinear or a branched aliphatic or cyclic C₁-C₆-alkyl group, and A is aC₂H₄— or C₃H₆-group, alone or in combination with b) at least onehydroxy compound and/or c) at least one ether compound.
 2. The methodaccording to claim 1, wherein the hydraulic binders are cement, thelatent hydraulic binders are fly ash, blast furnace slag, burned oilshale, natural pozzolanas, or silicafume and the inert fillers are stonepowder.
 3. The method according to claim 1, wherein the shrinkagereducing agent is added in an amount of 0.001-6.0% by weight based onthe weight of the binder.
 4. The method according to claim 1, whereinthe shrinkage reducing agent is a powder, or a dispersion or an emulsionin water and/or in a non-aqueous solvent, or a solution in water and/orin a non-aqueous solvent.
 5. The method according to claim 1, whereinthe shrinkage reducing agent is applied pre-mixed with at least onehydraulic binder or in dry mortar or concrete.
 6. The method accordingto claim 1, wherein the shrinkage reducing agent is admixed to thebinder(s) during the production of the binder(s) in the factory eitherprior or during the grinding.
 7. The method according to claim 1,wherein the shrinkage reducing agent is added to the dry binder or thewater-admixed binder, mortar or concrete in the factory, at the buildingsite, in the mixing apparatus, in the delivery pump, or by means of astatic mixer with a powder dosing apparatus or a liquid dosing apparatusdirectly into the mixture.
 8. The method according to claim 1, whereinthe shrinkage reducing agent is added in an amount of 1 to 3% by weightbased on the weight of the binder.